In recent years, batteries capable of being charged and discharged are utilized in drive power sources of vehicles such as a hybrid vehicle and an electric vehicle and portable electronic devices such as notebook-sized personal computer and a video camcorder. One example of such batteries is a battery configured such that an electrode body (corresponding to a flat wound electrode body mentioned later) including a current collector (corresponding to an electrode sheet mentioned later) that is wound around a winding axis and formed in a flat oval or elliptic shape in cross section (for example a battery disclosed in Patent Document 1).